can't sleep

30 weeks pregnant and getting a full right painful leg cramp when I'm laying down. It's very painful and it lasts all day . When I'm laying down the pain strikes but during the day it's soar and I cripple when walking most of the time . I really can't sleep then night or tend to take my nap with my almost 2 year old . I'm very cranky and moody I barely get 3 hours of sleep a day . My Doc told me to take magnesium pills and drink water . That's not helping lol sorry for the long msg but had to let it out . Whose up ? lol it's 5:58am by me